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How Calendars Gave Numbers Meaning
How counting days, moons and years in calendar systems tied particular numbers such as 7, 12, 19, 60 and 260 to ritual, rule and the shape of cultural life.
Scripture, Letters and Calendars
Calendars and Cycles of Time
How weeks, months and long cycles gave particular numbers a place in culture.
Egyptian Decans and the Division of the Day
How the ancient Egyptian decan stars, thirty-six groups marking ten-day intervals, helped shape a night of twelve hours and the later twenty-four hour day.
Hindu Yugas and Cosmic Ages
The four Hindu yugas, Krita, Treta, Dvapara and Kali, and the huge figures such as 4,320,000 years that Puranic texts use to measure cosmic time.
Leap Years and the Gregorian Reform
Why the Julian calendar drifted, how Pope Gregory XIII's 1582 reform dropped ten days and refined leap years, and why countries adopted it centuries apart.
Origins of the Seven-Day Week
How Babylonian month counts, the Jewish Sabbath and Roman planetary astrology each contributed to the seven-day week and the names of its days.
The Chinese Sexagenary Cycle
How ten heavenly stems and twelve earthly branches combine into a sixty-term cycle used to name years, months and days in China and neighbouring cultures.
The Hijri Calendar and the Twelve Lunar Months
How the purely lunar Islamic calendar counts twelve months of 29 or 30 days, why its year is 354 or 355 days, and how the Quran shapes the rule.
The Maya Long Count
How the Maya Long Count counted days in baktuns, katuns and tuns from a fixed starting point, and why its 2012 turnover was misread as a prophecy of doom.
The Metonic Cycle and Nineteen Year Calendars
Why 235 lunar months almost exactly equal 19 solar years, and how this Metonic relationship shaped Babylonian, Greek, Jewish and Easter calendars.
The Roman Calendar and Its Twelve Months
From the traditional ten-month year of Romulus to Numa's added months and Julius Caesar's 46 BCE reform, how Rome arrived at a twelve-month year.
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